The current invention relates to acoustic signal processing in general, and specifically to a method and system for silencing music and other background sounds in a noisy environment.
In the specification and claims which follow below, the term “noisy environment” is intended to have equivalent meaning to “noisy room”, “noisy surroundings”, and/or “noising background”. Examples of noisy surroundings include, but are not limited to: restaurants, public places, and wedding halls.
In the specification and claim which follow below, the term “earpiece” is intended to have the same meaning of words such as, but not limited to: earphone, earphones, earbud, and hearing aid. The meaning of “noise” in the specification and claims which follow below is intended to mean any spurious sound, either in acoustic or electronic form, the spurious sound such as but not limited to: music; environmental sound; and undesirable conversation.
The “cocktail party effect” is the phenomenon of being able to focus one's auditory attention on a particular stimulus while filtering out a range of other stimuli, much the same way that a partygoer can focus on a single conversation in a noisy room. This effect is what allows most people to “tune into” a single voice and “tune out” all others. It may also describe a similar phenomenon that occurs when one may immediately detect words of importance originating from unattended stimuli, for instance hearing one's name in another conversation.
Most people can carry on conversations, even in a noisy environment, i.e. the “cocktail party effect”. Noisy surroundings are common. For example, many restaurants, halls, and large public places play music while guests attempt to converse with one another.
However, hearing loss or impairment, especially associated with age-related hearing loss, makes it difficult to hear/discern conversations in a noisy environment. This difficulty impacts the social life of those who cannot converse effectively in noisy surroundings. Hearing aids cannot typically correct this problem, as the issue is not to amplify the conversation sound but rather to distinguish the conversation-of-interest from other noise in the surroundings. One way to deal with the problem is as described below.
Active noise control (ANC), also known as noise cancellation, or active noise reduction (ANR) are methods for reducing unwanted sound by the addition of a sound, the additional sound specifically designed to cancel the unwanted (first) sound. An early example of a prior art publication in this field, and which is incorporated by reference, is that in which Paul Leug, Kirchstrasse, in German Patent Application 714,582 describe how sound oscillations, which are to be silenced, are taken in by a receiver and reproduced by a reproducing apparatus in the form of sounds having an opposite phase.
Reference is currently made to FIG. 1, which is a schematic representation of a prior art principle of ANC/ARC 5, showing a noise signal 6, an anti-noise signal 7, and a resultant sound signal 9. As is shown in the figure, anti-noise signal 7 is combined with noise signal 6 to yield the resultant sound signal, which has attenuated noise and/or an overall attenuated signal.
In general, active noise cancelation is a complicated problem to address; however cancelling noise in a specific location (such as in or very close to the human ear) is well known. One example of prior art developed to cancel a specific sound from the surroundings, within an ear, is the “Here One” product, by Doppler Labs Inc., 1958 South 950 East Provo, Utah 84606, USA, whose disclosure is incorporated herein by reference.
Reiterating, the issue is not to compensate for hearing loss, but to reduce background sounds, such as described by Jorgensen et al. in US patent application publication 20090041260, whose disclosure is incorporated herein by reference. Jorgensen describes a hearing device system comprising at least one hearing aid circuitry and at least one active noise cancellation unit, the at least one hearing aid circuitry comprises at least one input transducer adapted to convert a first audio signal to an electric audio signal; a signal processor connected to the at least one input transducer and adapted to process said electric audio signal by at least partially correcting for the hearing loss of a user; an output transducer adapted to generate from at least said processed electric audio signal a sound pressure in an ear canal of the user, whereby the generated sound pressure is at least partially corrected for the hearing loss of the user; the at least one active noise cancellation unit being adapted to provide an active noise cancellation signal adapted to perform active noise cancellation of an acoustical signal entering the ear canal in addition to said generated sound pressure, wherein the hearing device system further comprises a combiner unit adapted to combine the processed electric audio signal with the active noise cancellation signal, to obtain a combined signal and to provide the combined signal to the output transducer.
In U.S. patent application Ser. No. 13/559,299, whose disclosure is incorporated herein by reference, Christoph describes an active noise reduction system, which includes an earphone with a cup-like housing, and a transmitting transducer, which converts electrical signals into acoustical signals and is arranged at an aperture of the housing. A receiving transducer converts acoustical signals into electrical signals, and is arranged proximate the transmitting transducer. A duct includes an end acoustically coupled to the receiving transducer, another end located proximate the transmitting transducer. An acoustical path extends from the transmitting transducer to a listener's ear, and has a first transfer characteristic. Another acoustical path extends from the transmitting transducer through the duct to the receiving transducer, and has a second transfer characteristic. A control unit generates a noise reducing electrical signal that is supplied to the transmitting transducer. This signal is derived from the receiving-transducer signal and filtered with a third transfer characteristic.
Andrea et al., in U.S. Pat. No. 6,061,456, whose disclosure is incorporated herein by reference, describe a transducer for use in a noise cancellation apparatus for reducing background noise, including a housing having first microphone means for receiving a first acoustic sound composed of speech originating from an operator operating the apparatus and background noise, and for converting the first acoustic sound to a first signal, and second microphone means arranged at a predetermined angle φ in close proximity with respect to the first microphone means for receiving a second acoustic sound composed of substantially the background noise and for converting the second acoustic sound to a second signal. The first and second microphones are connected to a differential amplifier means of the noise cancellation apparatus so as to obtain a signal representing substantially speech. The amplifier means is for receiving acoustic sounds from each microphone and has a first terminal and a second terminal, wherein the second terminal is grounded. The transducer further includes a transistor means for receiving and amplifying an AC signal representative of the audio input from each microphone; and means for filtering the amplified AC signal from the DC signal, so that the DC signal powers the amplifier means. Also disclosed is a method for calibrating an active noise reduction apparatus including a housing having a speaker to produce an acoustic anti-noise signal in the housing, a microphone to detect an external noise signal, and an amplitude adjustment means to calibrate the acoustic anti-noise signal to create a quiet zone in the housing for operation with an independent electrical assembly, wherein the apparatus is calibrated separately from the electrical assembly. The method includes the steps of: inputting the external noise signal received by the microphone to produce an anti-noise signal; transmitting to the speaker the anti-noise signal having an equal gain and opposite phase response to the external noise signal detected by the microphone; and balancing the gain and phase response of the anti-noise signal by the amplitude adjustment means located in the noise reduction apparatus to match the gain and phase response of the external noise signal to yield a theoretical zero hi the quiet zone.
A strong disadvantage of the prior art is that a conversation-of-interest is generally cancelled/attenuated/removed, along with environmental noise.
There is therefore a need to more effectively cancel and/or clean a noisy background and with high selectivity, while substantially not-attenuating at least one conversation-of-interest in the environment to enable the user to more easily hear/discern the conversation.